保护层开采被保护层裂隙分布与增透效果相似材料模拟

Simulated study for the crack distribution and the antireflection effect with the mining of the protective layer

保护效果是保护层开采方案设计的重要依据,为了研究保护层开采时被保护层的裂隙发育特征与卸压增透效果,以相似材料试验模型为基础,设计了保护层开采被保护层渗透性箱式可伸缩式测试系统,包括进气系统、可伸缩箱式渗透特性测试系统和集气系统三部分,以长平煤矿保护层开采为例,开展了保护层开采渗透性测试试验。结果表明:保护层开采过程中,覆岩裂隙发育至被保护层直接顶范围,被保护层地层应力得到有效释放,充分采动区卸压系数为27.8%~32.2%,最高达46.9%;被保护层增透效果与采动应力呈负相关关系,原岩应力区渗透率不变,支承应力区渗透率降低8%~56%,卸压区渗透率增大14.5倍;随工作面推采,卸压区域逐渐扩展,被保护层增透区域也逐渐增大。最后,根据试验结果讨论了试验系统的缺点及改进建议,为下一步的研究提供指导。

The paper is mainly engaged in a study of the fracture development characteristic features and the effect of the pressure relief and permeability enhancement in the mining of the protective layer,which serves as the protective effect on the part of theprotective mining scheme.As a matter of fact,based on the similar material experiments,a box-type retractable testing system has been already designed for the permeability of the protected layer in the protective mining layer.The retractable testing system is actually made up of three parts:the intake system,the telescopic box permeability testing system and the gas collecting system.Taking the protective mining layer of Changping Coal Mine(Beijing suburb)for example,we have conducted the permeability experiment with the protective mining layer.In the abovementioned mining process of the protective layer,the overburdened fissures tend to develop to the immediate top of the protected layer,whereas the stratum stress of the protected layer can be effectively released.In doing so,the coefficient of the pressure relief in the fully mining area may tend to range from^27.8%to 32.2%,while the maximum range area rate can be made to reach 46.9%.And,then,on the contrary,the permeability of the protected layer tends to be negatively correlated with the mining stress,though the permeability of the original rock stress zone remains unchanged.As the permeability of the supporting stress zone decreases by 8%-56%,the permeability of the relief zone would like to increase by 14.5 times.With the mining progress going on along with the working face,the pressure relief area would also expand gradually,and,in turn,the permeability enhancement area of the protected layer tends to advance gradually,too.Thus,the theoretical analysis method can be taken to verify and analyze the advancing features of the overburdened part,so as to promote the progressive results well in accord with the similar simulations.Hence,eventually,the shortcomings of the experimental system and the suggestions for improvement have to be properly discussed and corresponding guidance for further research can surely be offered from the experimental results.